Re: Dimmable fluorescent light, a soultion is required.

[Richard Malcolm-Smith <rich@xxxxxxx>]

Stuart Poulton wrote:

> Does anyone have any details and hopefully costings on dimmable
> fluorescent lighting ?
>
> Also, is it possible to control such lighting using C-Bus or Polaron ?

To dim fluros signifigantly, you need to make the heaters at the ends of
the
tubes run all the time.

If dimming to 70% or so is ok, it can be done, Get either a 3 wire dimmer
(Most
high power ones) or run a small incandesant light on the dimmer too.

Also, you must remove all the power factor correction capacitors from the
fluro
fitting.

If you dim too much, the tube will go out, and the starter will close to
try to
re-strike the tube. Dont leave it like this or you will blacken the
ends/kill
the tube, the preheat on a starter based fluro fitting is enough to get the
ends
glowing, and tubes dont last long in that state.

If you need more dimming, there are what are called filiment transformers,
These
take the full 240 volt, and develop a seperate DC source to drive the
heaters at
a sane amount. You need both dimmed and undimmed 240 at the fitting. These
are
wired with the 2 secondarys across the 2 ends of the tubes, and are powered
from
the undimmed 240 volt. When these are fitted, turning the light on will
gradually flicker up to full brightness over about 5 seconds when first
turned
on, like the old fasioned fittings with no starters (Because it drives the
tube
just like that) - keeping the heaters on wastes power, and some say reduced
tube
life, but mine seem to last fine.

Apparantly this will not work with the now more common slim tubes, but I
have a
stash of old fat 5 foot warm white ones so thats not an issue for me.

I can get 10 steps of dim on the X10, the 5 below that, the arc collapses
and it
just has a faint glow. The switching of the undimmed is done with a nasty
diode-capacitor-relay setup that buzzes sometimes, but hey, it works. Im
thinking of replacing it with a dolid state relay but why fix what works.

Anything that can drive incandesant loads should be able to drive the
fluros,
but if it gets the zero crossing from the mains and not the load (like the
x-10
ones) the inductive nature will mess it up at low levels. You will also
most
likly need a resitive load on it to hold the dimmer on, since the arc
doesnt
start straight away. 3 wire dimmers normally hold the triac on for the
duration
rather then pulse it, but you never know till you try it.


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